D. ‘Manage by exception’, because it uses an assurance mechanism so that the project board can be confident controls are effective. This principle allows for efficient use of senior management time and clear lines of accountability and decision making. It ensures that the project board is only involved in decision making when a proposed change exceeds the agreed tolerances. Otherwise, the change authority has the responsibility to review, reject or approve requests for change within delegated limits. This way, the project board can focus on strategic decisions while day-to-day management is delegated to the Project Manager.